1. Field of the Invention
This invention relates to velocipedes. More specifically, the present invention relates to crank arm extenders for velocipedes.
2. Description of the Prior Art
Achieving optimum performance on a bicycle depends significantly on properly fitting the bicycle to the cyclist. Naturally, the position of the cyclist relative to the handle bars and pedals is important to extracting maximum output with minimized discomfort. Additionally, the length of the pedalling stroke, as measured from apex to nadir, is crucial to balancing the cyclist's power with endurance. For example, some cyclists prefer a longer pedalling stroke for cycling up hills and prefer shorter ones for flat rides. The length of the pedalling stroke depends on the length of the crank arm; longer crank arms yield longer pedalling strokes. The stroke should be the same for each leg, absent physical necessity, to avoid erratic performance and discomfort.
Cyclists have at their disposal a wide range of one-piece crank arms having different sizes which may be interchanged. However, changing crank arms typically necessitates transferring the sprockets from the undesired crank arm to the desired crank arm and re-tuning the front derailleur, at a minimum. This is inconvenient.
Cyclists also have at their disposal a wide range of multiple-piece, crank arm extenders. Some are infinitely indexable, rendering them difficult to provide uniform pedalling strokes for each foot. Other crank arm extenders may be finitely indexable. However, typically these include complex mechanisms that add weight and failure modes to the bicycle. Still others simply do not lend themselves to universal adaptation to all bicycle crank arms. A need exists for simple, finitely indexable bicycle crank arm extender that is readily, universally and securably installable on a bicycle crank arm.
Several types of bicycle crank arm extenders are described in the patent literature. Unfortunately, as reviewed above, the apparatuses described provide complex mechanisms that add weight to a bicycle and/or do not readily adapt to all bicycle crank arms. For example, U.S. Pat. No. 625,986, issued May 30, 1899, to Frederick G. Pennock, describes an adjustable crank for velocipedes. The apparatus includes a square-shaped sleeve mounted on a crank shaft. The invention includes a crank with a shank portion and a tapered portion. A pedal mounts at the end of the tapered portion. A longitudinal, threaded bore is disposed at the end of the shank portion. The shank portion further has a square-shaped cross section that is slidingly received in the sleeve. A shoulder is disposed at the transition point between the tapered and shank portions. A leaf spring lays against one of the flat sides of the shank, extending therebeyond, and abuts the shoulder. The crank is slidingly adjusted within the sleeve and fixed therein by tightening a threaded fastener in the threaded bore against the free end of the spring. The spring is urged to bend and frictionally engage the sleeve. The extender is infinitely indexable.
U.S. Pat. No. 823,712, issued Jun. 19, 1906, to Bernhard Uhlmann, describes an adjustable pedal crank for bicycles. The device includes a two-piece crank with an inner piece that slides between two positions relative to and within an outer piece. The inner piece is fixed relative to the outer piece with lock means that may be selectably tripped with an eccentric mechanism.
U.S. Pat. No. 3,922,929, issued Dec. 2, 1975, to John L. Marchello, describes a bicycle pedal crank extender. The apparatus includes an elongated member having a transverse slot and a transverse flange which, in cross section, has a U shape. The bicycle crank arm is slidingly received between the legs of the flange. A threaded fastener is received through the slot and threadingly engages with the distally-disposed threaded bore of the crank arm, clampingly securing the elongated member to the crank arm. The elongated member further has a threaded bore for receiving the pedal. The extender is infinitely indexable.
U.S. Pat. No. 4,648,287, issued Mar. 10, 1987, to Jay Preskitt, describes a pedal stroke adjuster for a bicycle or exercise machine. The device includes an elongated member that mounts permanently onto a bicycle crank arm. The elongated member has an elongated, transverse slot in which an adjuster block slides. The transverse slot has a plurality of notches disposed in one side of the slot. The adjuster member has spring-loaded latch means that is selectably inserted into one of the slots, fixing the adjuster block relative to the elongated member.
U.S. Pat. No. 4,850,245, issued Jul. 25, 1989, to Nicholas G. Feamster et al., describes a bicycle crank and pedal structure. The apparatus includes an elongated tube having an inner end and an outer end. A plurality of transverse throughbores are disposed along the length of the tube. A pedal is rotatably mounted on the outer end of the tube. The tube further has a pair of threaded bores which receive threaded fasteners. The crank arm is inserted in the tube, a threaded fastener passes through one of the throughbores in the tube along with the distally-disposed threaded bore of the crank arm, fixing the tube relative to the crank arm. The threaded fasteners are tightened against the crank arm, deterring play between the crank arm and tube.
U.S. Pat. No. 4,882,945, issued Nov. 28, 1989, to Jose Trevizo, describes a pedal extension device. The device includes a sleeve member that slidingly receives a telescoping rod. A pedal is rotatably mounted on the telescoping rod. The invention includes cam means that slides the telescoping member, adjusting the length thereof, corresponding to the rotation of the pedal. The telescoping member is adjusted outwardly during half of a revolution and adjusted inwardly during the second half of the revolution.
U.S. Pat. No. 4,915,374, issued Apr. 10, 1990, to K. Richard Watkins, describes a recumbent exercise cycle with articulated pedals. The invention includes a two-piece crank arm. A first elongated member having a plurality of transverse bores is mounted on the crank shaft. A second elongated member, having a plurality of transverse throughbores, includes a sleeve mounted at one end. The sleeve receives the first elongated member. The sleeve has a transverse bore that receives a bolt. The bolt, received in one of the plurality of transverse bores of the first elongated member, fixes the first elongated member relative to the second elongated member. A pedal is rotatably mounted in one of the transverse throughbores of the second elongated member.
U.S. Pat. No. 5,161,430, issued Nov. 10, 1992, to Richard W. Febey, describes a pedal stroke range adjusting device. The device includes an elongated frame that mounts on a bicycle crank arm. The mounting means include a threaded fastener that is received in the distally-disposed throughbore of the crank arm and threadingly engages with a threaded bore in the frame. The mounting means also includes a pair of threaded fasteners that are received in transverse throughbores in the frame and engage threaded bores of a transverse bar member. The frame includes a pair of parallel, longitudinal flanges that define a slot. A plurality of bores are disposed along the slot. A block member is slidingly received within the slot. The block member includes a latch member that is received in one of the plurality of bores, thus fixing the block member relative to the frame. A pedal is rotatably mounted on the block member.
French Patent No. 876,494, published Nov. 6, 1942, issued to Jules Warmont, shows a crank arm extender. The device includes a frame having parallel flanges. The frame has a throughbore which receives a threaded fastener. The threaded fastener engages with the distally-disposed threaded bore of the crank arm. The flanges restrain the frame from rotating about the throughbore. A pedal is rotatably mounted on the frame. The extender is not indexable.
English Patent No. 22,058, published Dec. 21, 1901, issued to Arthur Dean, describes a new or improved adjustable crank for use with velocipedes and for other purposes. The apparatus includes a two-piece crank arm. A first elongated member has a threaded bore. A second elongated member has external threads that engage the internal threads of the first elongated member. When the two members are threadingly indexed appropriately with respect to each other, a lock ring, slidingly received on the second elongated member, has teeth that engage with notches in the second elongated member, rotationally fixing the first and second elongated members. A nut, threadingly received on the second elongated member, is tightened against the ring.
Clearly, the above demonstrates a need for a simple, finitely indexable bicycle crank arm extender that is readily, universally and securably installable on a bicycle crank arm.
None of the above references, taken alone or in combination, are seen as teaching or suggesting the presently claimed bicycle crank arm extender.